Diffusive light-management films, including light-diffusive films, diffusive light-angle management films, and diffusive reflective polarizing films have been developed for visual displays such as liquid crystal device (LCD) displays. During the manufacture of the diffusive light-management films, film defects can occur that need to be detected.
Machine vision systems have been developed for determining defects in non-diffusive films, such as transparent films. The system propagates light through the film and then monitors the propagated light to determine if defects exist in the film. These systems, however, may not be able to detect defects in diffusive light management films as the light diffusion blurs the image of the defect. For example, if a defect is on a bottom surface of a light-management film and light propagates through a bottom surface of the film and outwardly from a top surface of the film, the film would diffuse the light as it propagates through the film. Accordingly, a camera disposed proximate the top surface of the film may not be able to detect the defect on the bottom surface of the film due to the light diffusion through the film.
There is thus a need for an improved machine vision system that can effectively detect defects in a light-management film.